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Specific saposin C deficiency: CNS impairment and acid beta-glucosidase effects in the mouse.

Sun Y, Ran H, Zamzow M, Kitatani K, Skelton MR, Williams MT, Vorhees CV, Witte DP, Hannun YA, Grabowski GA - Hum. Mol. Genet. (2009)

Bottom Line: Ultrastructural analyses revealed inclusions in axonal processes in the spinal cord, sciatic nerve and brain, but no excess of multivesicular bodies.Activated microglial cells and astrocytes were present in thalamus, brain stem, cerebellum and spinal cord, indicating regional pro-inflammatory responses.These results support the view that saposin C has multiple roles in glycosphingolipid (GSL) catabolism as well as a prominent function in CNS and axonal integrity independent of its role as an optimizer/stabilizer of GCase.

View Article: PubMed Central - PubMed

Affiliation: Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.

ABSTRACT
Saposins A, B, C and D are derived from a common precursor, prosaposin (psap). The few patients with saposin C deficiency develop a Gaucher disease-like central nervous system (CNS) phenotype attributed to diminished glucosylceramide (GC) cleavage activity by acid beta-glucosidase (GCase). The in vivo effects of saposin C were examined by creating mice with selective absence of saposin C (C-/-) using a knock-in point mutation (cysteine-to-proline) in exon 11 of the psap gene. In C-/- mice, prosaposin and saposins A, B and D proteins were present at near wild-type levels, but the saposin C protein was absent. By 1 year, the C-/- mice exhibited weakness of the hind limbs and progressive ataxia. Decreased neuromotor activity and impaired hippocampal long-term potentiation were evident. Foamy storage cells were observed in dorsal root ganglion and there was progressive loss of cerebellar Purkinje cells and atrophy of cerebellar granule cells. Ultrastructural analyses revealed inclusions in axonal processes in the spinal cord, sciatic nerve and brain, but no excess of multivesicular bodies. Activated microglial cells and astrocytes were present in thalamus, brain stem, cerebellum and spinal cord, indicating regional pro-inflammatory responses. No storage cells were found in visceral organs of these mice. The absence of saposin C led to moderate increases in GC and lactosylceramide (LacCer) and their deacylated analogues. These results support the view that saposin C has multiple roles in glycosphingolipid (GSL) catabolism as well as a prominent function in CNS and axonal integrity independent of its role as an optimizer/stabilizer of GCase.

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Pathology in cerebellum. (A) Anti-calbindin antibody stained Purkinje cells (brown) in 24-month-old C+/− and C−/− mouse brain. Loss of Purkinje cells in saposin C−/− mice progressed from cerebella lobule III to X with age. Increases of astrogliosis demonstrated by anti-GFAP antibody staining (brown) were in the region where the Purkinje cells were lost. Normal Purkinje cell layers and astrocytes were found in the C+/− cerebellum. (B) Calbindin staining revealed axon and neuronal processes in the molecular layer and white matter of the cerebellum. (B1) Normal Purkinje cells and axons (arrows) in C+/− mouse. (B2) Degeneration of Purkinje cell axons (stars) in the molecular layer of cerebella lobule X in 24-month-old C−/− mouse. (B3) Neuronal processes in C+/− cerebella white matter. (B4) Neural spheroids (arrows) presented in the neuronal processes of C−/− mouse. (C) 24-month-old C+/− and C−/− mouse cerebellum. The white bars show the height of cerebellum. The size of saposin C−/− cerebellum was reduced at 24 months. (D) Atrophy in the granule cell layer of saposin C−/− mice. NeuN staining cells (green) were decreased in the granulecell layer of cerebella lobule III from 24-month-old C−/− mice compared with lobule III of C+/− mouse. The white bar in the photo shows the diameter of the granule cell layer. Both GFAP (brown) and CD68 (brown) signals were enhanced in lobule III of the saposin C−/− mouse. Sections stained with calbindin and GFAP were counterstained with methyl green (green). CD68-stained sections were counterstained with hemotoxilin.
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DDP531F7: Pathology in cerebellum. (A) Anti-calbindin antibody stained Purkinje cells (brown) in 24-month-old C+/− and C−/− mouse brain. Loss of Purkinje cells in saposin C−/− mice progressed from cerebella lobule III to X with age. Increases of astrogliosis demonstrated by anti-GFAP antibody staining (brown) were in the region where the Purkinje cells were lost. Normal Purkinje cell layers and astrocytes were found in the C+/− cerebellum. (B) Calbindin staining revealed axon and neuronal processes in the molecular layer and white matter of the cerebellum. (B1) Normal Purkinje cells and axons (arrows) in C+/− mouse. (B2) Degeneration of Purkinje cell axons (stars) in the molecular layer of cerebella lobule X in 24-month-old C−/− mouse. (B3) Neuronal processes in C+/− cerebella white matter. (B4) Neural spheroids (arrows) presented in the neuronal processes of C−/− mouse. (C) 24-month-old C+/− and C−/− mouse cerebellum. The white bars show the height of cerebellum. The size of saposin C−/− cerebellum was reduced at 24 months. (D) Atrophy in the granule cell layer of saposin C−/− mice. NeuN staining cells (green) were decreased in the granulecell layer of cerebella lobule III from 24-month-old C−/− mice compared with lobule III of C+/− mouse. The white bar in the photo shows the diameter of the granule cell layer. Both GFAP (brown) and CD68 (brown) signals were enhanced in lobule III of the saposin C−/− mouse. Sections stained with calbindin and GFAP were counterstained with methyl green (green). CD68-stained sections were counterstained with hemotoxilin.

Mentions: Loss of Purkinje cells in the cerebellum was evident at 2 months and progressed chronologically from lobule III to X, demonstrated by anti-calbindin antibody staining (Fig. 7A), such that by 24 months Purkinje cells were absent in lobules III to VIII. Calbindin staining revealed the degeneration of Purkinje cell axons in molecular layers and the appearance of spheroids in neuronal processes in cerebellar white matter of saposin C−/− mice (Fig. 7B). In addition, granule cell atrophy was demonstrated by decreased NeuN-stained cells in the granule cell layer (Fig. 7D). The Purkinje cell loss was subsequent to granule cell atrophy. Cerebellar reduction in C−/− was particularly evident at >20 months (Fig. 7A and C). In the same regions, increases in astrogliosis and activated microglial cells were evident (Fig. 7D).


Specific saposin C deficiency: CNS impairment and acid beta-glucosidase effects in the mouse.

Sun Y, Ran H, Zamzow M, Kitatani K, Skelton MR, Williams MT, Vorhees CV, Witte DP, Hannun YA, Grabowski GA - Hum. Mol. Genet. (2009)

Pathology in cerebellum. (A) Anti-calbindin antibody stained Purkinje cells (brown) in 24-month-old C+/− and C−/− mouse brain. Loss of Purkinje cells in saposin C−/− mice progressed from cerebella lobule III to X with age. Increases of astrogliosis demonstrated by anti-GFAP antibody staining (brown) were in the region where the Purkinje cells were lost. Normal Purkinje cell layers and astrocytes were found in the C+/− cerebellum. (B) Calbindin staining revealed axon and neuronal processes in the molecular layer and white matter of the cerebellum. (B1) Normal Purkinje cells and axons (arrows) in C+/− mouse. (B2) Degeneration of Purkinje cell axons (stars) in the molecular layer of cerebella lobule X in 24-month-old C−/− mouse. (B3) Neuronal processes in C+/− cerebella white matter. (B4) Neural spheroids (arrows) presented in the neuronal processes of C−/− mouse. (C) 24-month-old C+/− and C−/− mouse cerebellum. The white bars show the height of cerebellum. The size of saposin C−/− cerebellum was reduced at 24 months. (D) Atrophy in the granule cell layer of saposin C−/− mice. NeuN staining cells (green) were decreased in the granulecell layer of cerebella lobule III from 24-month-old C−/− mice compared with lobule III of C+/− mouse. The white bar in the photo shows the diameter of the granule cell layer. Both GFAP (brown) and CD68 (brown) signals were enhanced in lobule III of the saposin C−/− mouse. Sections stained with calbindin and GFAP were counterstained with methyl green (green). CD68-stained sections were counterstained with hemotoxilin.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2807372&req=5

DDP531F7: Pathology in cerebellum. (A) Anti-calbindin antibody stained Purkinje cells (brown) in 24-month-old C+/− and C−/− mouse brain. Loss of Purkinje cells in saposin C−/− mice progressed from cerebella lobule III to X with age. Increases of astrogliosis demonstrated by anti-GFAP antibody staining (brown) were in the region where the Purkinje cells were lost. Normal Purkinje cell layers and astrocytes were found in the C+/− cerebellum. (B) Calbindin staining revealed axon and neuronal processes in the molecular layer and white matter of the cerebellum. (B1) Normal Purkinje cells and axons (arrows) in C+/− mouse. (B2) Degeneration of Purkinje cell axons (stars) in the molecular layer of cerebella lobule X in 24-month-old C−/− mouse. (B3) Neuronal processes in C+/− cerebella white matter. (B4) Neural spheroids (arrows) presented in the neuronal processes of C−/− mouse. (C) 24-month-old C+/− and C−/− mouse cerebellum. The white bars show the height of cerebellum. The size of saposin C−/− cerebellum was reduced at 24 months. (D) Atrophy in the granule cell layer of saposin C−/− mice. NeuN staining cells (green) were decreased in the granulecell layer of cerebella lobule III from 24-month-old C−/− mice compared with lobule III of C+/− mouse. The white bar in the photo shows the diameter of the granule cell layer. Both GFAP (brown) and CD68 (brown) signals were enhanced in lobule III of the saposin C−/− mouse. Sections stained with calbindin and GFAP were counterstained with methyl green (green). CD68-stained sections were counterstained with hemotoxilin.
Mentions: Loss of Purkinje cells in the cerebellum was evident at 2 months and progressed chronologically from lobule III to X, demonstrated by anti-calbindin antibody staining (Fig. 7A), such that by 24 months Purkinje cells were absent in lobules III to VIII. Calbindin staining revealed the degeneration of Purkinje cell axons in molecular layers and the appearance of spheroids in neuronal processes in cerebellar white matter of saposin C−/− mice (Fig. 7B). In addition, granule cell atrophy was demonstrated by decreased NeuN-stained cells in the granule cell layer (Fig. 7D). The Purkinje cell loss was subsequent to granule cell atrophy. Cerebellar reduction in C−/− was particularly evident at >20 months (Fig. 7A and C). In the same regions, increases in astrogliosis and activated microglial cells were evident (Fig. 7D).

Bottom Line: Ultrastructural analyses revealed inclusions in axonal processes in the spinal cord, sciatic nerve and brain, but no excess of multivesicular bodies.Activated microglial cells and astrocytes were present in thalamus, brain stem, cerebellum and spinal cord, indicating regional pro-inflammatory responses.These results support the view that saposin C has multiple roles in glycosphingolipid (GSL) catabolism as well as a prominent function in CNS and axonal integrity independent of its role as an optimizer/stabilizer of GCase.

View Article: PubMed Central - PubMed

Affiliation: Division of Human Genetics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.

ABSTRACT
Saposins A, B, C and D are derived from a common precursor, prosaposin (psap). The few patients with saposin C deficiency develop a Gaucher disease-like central nervous system (CNS) phenotype attributed to diminished glucosylceramide (GC) cleavage activity by acid beta-glucosidase (GCase). The in vivo effects of saposin C were examined by creating mice with selective absence of saposin C (C-/-) using a knock-in point mutation (cysteine-to-proline) in exon 11 of the psap gene. In C-/- mice, prosaposin and saposins A, B and D proteins were present at near wild-type levels, but the saposin C protein was absent. By 1 year, the C-/- mice exhibited weakness of the hind limbs and progressive ataxia. Decreased neuromotor activity and impaired hippocampal long-term potentiation were evident. Foamy storage cells were observed in dorsal root ganglion and there was progressive loss of cerebellar Purkinje cells and atrophy of cerebellar granule cells. Ultrastructural analyses revealed inclusions in axonal processes in the spinal cord, sciatic nerve and brain, but no excess of multivesicular bodies. Activated microglial cells and astrocytes were present in thalamus, brain stem, cerebellum and spinal cord, indicating regional pro-inflammatory responses. No storage cells were found in visceral organs of these mice. The absence of saposin C led to moderate increases in GC and lactosylceramide (LacCer) and their deacylated analogues. These results support the view that saposin C has multiple roles in glycosphingolipid (GSL) catabolism as well as a prominent function in CNS and axonal integrity independent of its role as an optimizer/stabilizer of GCase.

Show MeSH
Related in: MedlinePlus